There are at least two usages of this term in various anime: Dragonite is the name of a powerful Pokemon, and the name of a rare substance in Outlaw Star.
Dragonite is the substance by which faster than light transport is possible. Originally found in a meteorite that crashed into a desert in China, dragonite allowed the initial development of a FTL drive, and spurred on the subsequent expansion into the galaxy, in a manner similar to the California Gold Rush. It seems that, when activated in a particular way, dragonite releases a vast quantity of energy which allows the FTL drive to do its thing.
Dragonite is the most valuable and rare substance in the galaxy, and is commonly used as a form of payment, similiar to how gold or a briefcase full of $100 bills is today. In Episode 16 "Demon of the Water Planet", the crew
of the Outlaw Star recovers a cargo ship that was full of dragonite: the estimated value was equivalent to the entire budget of all the frontier worlds (several hundred planets) for the next 5 years. Unfortunately for them, the dragonite ended up being of poor quality, and was only worth a few million Won, which barely covered the costs incurred during the operation. In another episode, the crew is paid for services rendered (saving a military base from a pirate sneak attack) with a small case of dragonite.
Dragonite is a powerful Pokemon, first encountered by Ash and crew in the Orange Islands. A Dragonite is a large (roughly 10-12 feet tall) yellow-orange dragon-like beast, with small wings (though apparently a Dragonite can still fly incredibly fast). In a 6 on 6 match, Ash barely
defeated the champion of the Orange Islands, who had a Dragonite among his Pokemon. The final blow was dealt by Pikachu, but Ash wouldn't have had a chance without Charizard, who was Ash's only Pokemon who could compare with Dragonite in terms of size and power.
A Dragonite was actually featured in an episode in the first season, but in this case it was gigantic (roughly 200 feet tall), and was never shown as anything more than a shadow in the mist.
Sorry, I don't know his Poke-stats or whatever they're called in the various card and video games; I just watch the cartoon.